Highly activated hydrogen containing material and method for producing the material

ABSTRACT

A hydrogen containing material comprises a first compound including hydrogen containing material and fluoride, and a second compound including a metal which becomes highly reactive with hydrogen when the metal becomes a compound including fluorine, and a compound including fluorine. The first compound and the second compound are integrally formed into a one-piece layer on the surface of the hydrogen containing material. The metal which becomes highly reactive with hydrogen when the metal becomes a compound including fluorine is at least one metal selected from a rare earth metal, rare earth alloy, Fe, Al, Mg, Ca, Mn, Zn, Zr, Li, or alloys comprising these elements.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a hydrogen containing materialand to a method for producing the material, and more particularlyrelates to a hydrogen containing absorbing material which is highlyactivated with hydrogen so as to be used as the negative pole materialof the nickel-hydride cell, medium for storing and transportinghydrogen, catalyst for hydrogenizing carbon oxide and for converting itto hydrocarbon, medium for energy conversion, medium for recoveringhydrogen gas from low concentration hydrogen gas and for purifying thehydrogen gas, and others, and to have the protective effect against thepoison of the poisonous material (hereinafter called poisoningrestraining effect).

[0002] The hydrogen containing (absorbing) material reversibly absorbsand discharges hydrogen by the treatment of heating, cooling,decompressing or pressuring thereof. Therefore, the hydrogen containingmaterial is expected to become a storing material of hydrogen as afuture secondary energy. Recently, the hydrogen containing alloy is usedas the negative pole material of nickel-hydride cell and expected as afuture high quality battery for the electric motor vehicle.

[0003] In order to stably cause the hydrogen containing material toabsorb and discharge the hydrogen, it is necessary to carry out theinitial hydrogenation treatment at high temperature, or high pressure,or high vacuum. For example, in the case of Mg—Ni alloy as the hydrogencontaining material, the reaction vessel is evacuated at 350° C., andthe absorbing and discharging of hydrogen must be repeated over 10 timesat 2-5 MPa. In the case of La—Ni alloy or La—Ni—Al alloy as the hydrogencontaining material, the reaction vessel is evacuated at 80-100° C., andthe absorbing and discharging of hydrogen is repeated over 10 times at1-3 MPa. In order to keep the surface of the hydrogen containing alloyin very high active condition, the alloy must not be contacted with air.If the alloy is exposed to the air, the alloy is immediately oxidized sothat the dissociation from hydrogen element to hydrogen atom isinhibited. Further, the hydrogen activity characteristic of the hydrogencontaining alloy is remarkably reduced by a particle impurity gasesincluded in the hydrogen gas such as CO, CO₂, O₂, H₂O, NH₃ and others.

[0004] Japanese Patent Publication 3-12121 discloses a microcapsulemethod of copper or nickel by the electroless plating in order toimprove the thermal conductivity of the hydrogen containing material andto protect the material from impurity gases other than the hydrogen gas.

[0005] The Japanese Patent Application Laid Open Publication 5-213601discloses treatment methods for highly activating and stabilizing thehydrogen containing material by treating the surface of the materialusing the supersaturation aqueous solution consisting of the fluoridemetallic compound including alkali metal.

[0006] The Japanese Patent Application Laid Open Publication 8-9504discloses material for hydrogen containing alloy which material iscoated with electroconductive powder and cuprous oxide powder and withoxidation inhibitor by mixing the powder for hydrogen containing alloy,conductive powder, and cuprous oxide powder with a high energy mixer, inorder to improve the initial hydrogenation characteristic and tomaintain the characteristic for a long term, and discloses a method forproducing the material.

[0007] However, none of the materials and method is proper for massproduction on account of the installation cost, production efficiencyand production cost. Although it is confirmed that the material has aprotective effect against impurity gases other than the hydrogen of thehydrogen containing material, there are problems in stability anddurability of the surface treatment layer at the absorbing anddischarging of hydrogen.

[0008] At present, a hydrogen containing alloy is used for the negativepole material of the small secondary battery, and almost all alloys areAB₅ alloys of the rare earth. As typical alloys, polyatomic alloyswherein the element A is La or rare earth metal alloys Mm (Misch-metall)and the element B is alloy produced by substituting Ni and a part of Niwith other elements (Co, Al, Mn, Si, Cr, Zr and others) are used. Forexample, there is alloys NaNi₅, MmNi_(2.5), LaNi_(4.7)Al_(0.3) andMmNi_(4.5)Mn_(0.3)Al_(0.2). The composing elements and composition ratioare selected in accordance with the using conditions. The hydrogencontaining alloy is used not only for the secondary battery, but alsofor the chemical heat pump which uses the storage and the purificationof hydrogen gas and the reaction heat of the alloy.

[0009] The reason why the rare earth AB₅ alloy is substantially used isthat the alloy can be initially activated with ease, has a greatpoisoning restraining effect, and can be easily treated compared withother alloys. However, the alloy is poor in durability. Morespecifically, the absorbing quantity of hydrogen reduces as theabsorbing and discharging cycle increases. The alloy can not be usedmore than several thousand times. Therefore, although the alloy has adurability necessary for the negative pole material of the secondarybattery, it is difficult to use the alloy for other fields which requiremuch longer durability. Furthermore, there is a problem that thereduction rate of durability of the alloy further increases in theatmosphere at a temperature more than 150° C.

[0010] As hydrogen containing alloys having at least one of thedurability and a high hydrogen containing capacity, and having apossibility for highly balancing both the characteristics, there istitanium-base hydrogen containing alloy, zirconium-base hydrogencontaining alloy, and vanadium-base hydrogen containing alloy, andothers. However in spite of the fact that these alloys have the abovedescribed characteristic and do not deteriorate at high temperature,there are considerable number of alloys having difficulty in initialactivation and sensitivity influenced by poisoning (atmosphere exposure,impurity gases in hydrogen gas such as CO, H₂O, O₂, H₂S). As a result,these alloys can not exercise their inherent performance, and hence haveproblems in treatment thereof.

[0011] In order to improve reactivity, durability, hydrogen dissociationpressure-composition isothermal characteristic, and initialhydrogenation characteristic, polyatomic alloys are developed, whichalloy is produced by substituting a part of a basic hydrogen containingalloy with another element. For example, a part of an alloy such as rareearth-base alloy, magnesium-base alloy, titanium-base alloy,zirconium-base alloy, or calcium-base alloy is substituted with anothersingle element such as Al, Mn, Cr, Fe, or Cu, or with plural elements.However, an alloy having a remarkable protective effect against animpurity other than hydrogen is not developed.

[0012] In order to resolve the above described problems in theconventional alloys, the inventors of the present invention proposedhighly activated hydrogen containing materials and the method forproducing the materials, wherein on a surface of hydrogen containingalloy such as rare earth-base alloy, magnesium-base alloy, titanium-basealloy, zirconium-base alloy, or calcium-base alloy, a compound layerincluding fluorine is formed so as to highly activate the hydrogencontaining alloy with hydrogen.

[0013] For example, in Japanese Patent Publication No. 2835327, there isdisclosed a method for highly activating and for stabilizing thehydrogen containing material, wherein a hydrogen containing material anda hydrofluoric anhydride solution are contacted with each other so thata metallic fluoride film of the metal composition of the hydrogencontaining material itself is formed on the material.

[0014] In the Japanese Patent Application Laid Open Publication10-219301, there is disclosed a highly activated hydrogen containingmaterial and a method for producing the material, wherein a hydrogencontaining material including at least one of elements Al, Fe, Mg, Ca,Mn, Zn, Zr, and Li is fluorinated, thereby forming a fluoride of themetal on the surface or in a surface layer of the hydrogen containingmaterial.

[0015] Furthermore in the Japanese Patent Application Laid OpenPublication 10-219301, there is a disclosed highly activated hydrogencontaining material and a method for producing the material, wherein ametal which becomes high active with hydrogen when fluorinated ispreliminarily coated in the-hydrogen containing material, thereafter thecoating metal is fluorinated or treated so as to become fluoride. As aresult, the hydrogen containing material becomes active with hydrogen.

[0016] In accordance with the method described in the Japanese PatentNo. 2835327, it is possible to highly activate and stabilize thehydrogen containing material without a large installation andcomplicated steps. Therefore, the method has an advantage inmass-producing. However, there also exists a hydrogen containingmaterial wherein a fluoride layer can not be formed on the material, oreven if a fluoride layer can be formed on the material, the fluoridelayer is impossible to become high active with hydrogen, because of thekind of the hydrogen containing material.

[0017] The former highly activated material and the producing methoddescribed in the Japanese Patent Publication 10-219301, has the sameadvantage as that of the Japanese Patent Publication No. 2835327.However, the metal which becomes high active is included in the hydrogencontaining material itself. Therefore, only metals exposed on thesurface of the hydrogen containing material are effective. If a smallamount of a high active fluoride exists on the surface of the hydrogencontaining material, the material has an effect though the amount issmall. However, in the absorption and discharge reaction whichaccompanies a surface reaction, and in the methanization reaction whichreacts H₂ with CO, CO₂ and others to them to hydrocarbon gas such asCH₄, it is more preferable that a large amount of active portion existson the surface. The hydrogen containing alloy is made into an alloycorresponding to the using condition of the alloy by adding anotherelement to a basic composition element or substituting, with anotherelement in accordance using temperature and pressure condition.Therefore, it is difficult to compose the hydrogen containing alloy onlyby metal which is highly activated by becoming fluoride. Consequently,such a hydrogen containing material can not be highly activated by theabove described producing method.

[0018] In the latter hydrogen containing material and the producingmethod, since the hydrogen containing material is coated with a fluorideof high activity with hydrogen regardless of the composition element,the hydrogen containing material has a high reactivity with hydrogen.However, the hydrogen containing material as the matrix and the fluoridecoating the material are basically different from each other in kind.Consequently, there may occur that the fluoride layer on the surface ofthe hydrogen containing material peels off because of expansion andcontraction of the material at the absorption and discharge of hydrogen.

SUMMARY OF THE INVENTION

[0019] Accordingly, an object of the present invention is to resolve theabove described problems in the prior arts, more particularly to providea hydrogen containing material having a hydride layer on the surface,which hydride layer has a high reactivity with hydrogen,,so that thehydrogen containing material is highly activated with hydrogen more thanthe inherent reactivity of the material despite a poisoning environment.

[0020] Another object of the present invention is to provide a hydrogencontaining material having a fluoride layer which is not peeled off fromthe surface so that it is possible to maintain a high reactivity withhydrogen for a long term, while at least one of characteristics that isthe durability of the hydrogen containing material itself and the highhydrogen absorbing capacity is maintained.

[0021] According to the present invention, there is provided a hydrogencontaining material the surface of which has layers comprising a firstcompound including the hydrogen containing material and fluorine, and asecond compound including a metal which becomes high reactive withhydrogen when the metal becomes a compound including fluorine and acompound including fluorine, wherein the first compound and the secondcompound are integrally formed into a one-piece layer on the surface ofthe hydrogen containing material.

[0022] The hydrogen containing material comprises an ingot, or powder ofa material or intermediate product or finished product of an alloyselected from a zirconium alloy, titanium alloy, vanadium alloy, rareearth alloy, and magnesium alloy.

[0023] Furthermore, the metal which becomes high reactive with hydrogenwhen the metal becomes a compound including fluorine is at least onemetal selected from a rare earth metal, rare earth alloy, Fe, Al, Mg,Ca, Mn, Zn, Zr, Li, or alloys comprising these elements.

[0024] The metal is melted in the fluorinating treatment liquid in ametal ion condition or in an ultrafine grain condition.

[0025] The fluorinating treatment liquid contacted with the hydrogencontaining material is heated so as to vaporize the liquid to dry thehydrogen containing material.

[0026] The metal which becomes high reactive with hydrogen when themetal becomes a compound including fluorine is at least one metalselected from a rare earth metal, rare earth alloy, Fe, Al, Mg, Ca, Mn,Zn, Zr, Li, or alloys comprising these elements.

[0027] The fluorinating treatment liquid is a hydrofluoric acid aqueoussolution or hydrofluoric anhydride solution, or solution composed by atleast one of organic compounds such as piridine, triethlamine andisopopyl alcohol, and hydrofluoric anhydride.

[0028] It is possible to select a desired thickness of the metalfluoride layer on the surface of the hydrogen containing material so asto extend to a desired depth in accordance with the use of the hydrogencontaining material.

[0029] In the hydrogen containing material of the present invention, inthe cases that a large amount of metals which become high active whenfluorinated are included in the basic composition elements, that a smallamount of metals which become high active are included in thecomposition elements, or that highly activated metal is not included, inany case, it is possible to form a large amount of very highly activatedfluoride layers, compared with a hydrogen containing material which issimply treated by fluorine, on the surface of the hydrogen containingmaterial.

[0030] In the boundary surface between the hydrogen containing materialas the matrix and the fluoride, a compound layer in which theconcentration of elements composing the matrix and the concentration ofthe fluoride are changed in inclined conditions is formed. The surfaceof the material is in the condition the fluoride of the matrix and thefluoride of the highly activated metal are mingled.

[0031] In another case, in the boundary surface between the hydrogencontaining material as the matrix and the fluoride, a compound layer inwhich the concentration of elements composing the matrix and theconcentration of the fluoride are gradually changed in inclinedconditions is formed, and the fluoride of the matrix is formed on theouter surface of the compound layer, and further on the outside of theouter surface, the fluoride of the highly activated metal is formed.

[0032] By forming the fluoride layer of metal the concentration of whichchanges in inclined condition, it is possible to prevent the metallicfluoride from exfoliating from the hydrogen containing material.Therefore, it is possible to maintain high activity with hydrogen for along term in spite of a poisoning environment, while maintaining atleast one of durability of the hydrogen containing material itself and alarge capacity for absorbing hydrogen.

[0033] Furthermore, in accordance with the method for producing hydrogencontaining material of the present invention, by contacting thetreatment liquid for fluorinating the metal and the hydrogen containingmaterial with each other, the metallic fluoride is formed on the surfaceor on the surface portion of the hydrogen containing material.Therefore, it is possible to produce the hydrogen containing material bya simple device with ease, and to correspond to the mass production.

[0034] These and other objects and features of the present inventionwill become more apparent from the following detailed description withreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0035]FIG. 1 is a graph showing the relationship between the timenecessary for absorbing hydrogen and the hydrogen concentration in theexample I;

[0036]FIG. 2 is a graph showing the change of the amount of hydrogenabsorption in the example I;

[0037]FIG. 3 is a graph showing the relationship between the timenecessary for absorbing hydrogen and the hydrogen concentration in theexample II;

[0038]FIG. 4 is a graph showing the relationship between the timenecessary for absorbing hydrogen and the hydrogen concentration in theexample III;

[0039]FIG. 5 is a photograph showing a surface condition of a hydrogencontaining material in the example I; and

[0040]FIG. 6 is a photograph showing a surface condition of a hydrogencontaining material in the comparative example 1C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0041] Hydrogen containing materials used in the present invention arehydrogen containable metals or alloys, in particular titanium alloys(titanium-base alloys), zirconium alloys, rare earth alloys, andmagnesium alloys. Specifically, for example, here is given as titaniumalloys, TiFe, TiCo, TiNi, TiMn₂, TiCr₂, TiV, as zirconiumalloys, ZrV₂,Zrcr₂, ZrMn₂, ZrFe₂, ZrCo₂, as rare earth alloys, LaNi₅,MmNi_(2.5)Co2.5, LaNi_(4.7)Al_(0.3), MmNi4.5Mn_(0.3)Al0.2,MmNi_(4.7)Al_(0.2)Zr_(0.1), LaNi_(4.5)Cr_(0.25)Mn_(0.25),M_(0.5)Ca_(0.5)Ni₅, as magnesium alloys, Mg₂Ni, Mg₂Cu.

[0042] In order to adjust and improve the dissociation pressurecharacteristic, plateau, hysteresis of the hydrogen containing material,polyelement alloys which are formed by addition or substitution of otherelements can be used.

[0043] Although the above described hydrogen containing materials areintermetallic compounds, vanadium alloys called as the solid solutionhydrogen containing alloy can be used. There are various alloys such as(V_(0.9)Ti_(0.1))_(0.8)Fe_(0.2), (V_(0.9)Ti_(0.1))_(0.9)Al_(0.1),(V_(0.85)Ti_(0.15))_(0.8)Mn_(0.2), V_(0.8)Ti_(0.2), V₃Mn_(0.4)Ni_(0.6).

[0044] As the metal which is formed on the surface of the hydrogencontaining material as the fluoride and has a high reactivity withhydrogen, there is given rare earth metal, alloy including rare earthmetal, Fe, Al, Mg, Ca, Mn, Zn, Zr, Li and alloys including these metals.As the rare earth metal, La and Mm are preferable. As alloy includingrare earth metal, AB₅ type alloy, which is hydrogen containing alloy,such as LaNi₅, and polyelement alloy in which a part Ni is substitutedwith another element (Al, Mn, Co, Cr, Si, Zr and others) can be used.

[0045] The rare earth alloy is not limited to above describedcomposition for the object of the present invention, and alloys ofnon-stoichiometry composition may be used.

[0046] As the A in the AB₅ type alloy, rare earth metal or rare earthmetal alloy other than La may be used, and as the B, elements other thanNi may be used. The alloy which has not hydrogen containing performancemay be used. Catalyst having a high reactivity with hydrogen excels incatalytic activity in proportion to the increasing of the surfaceactivity. As fluoride having a high surface acidity, there is givenFeF₂, AlF₃, MgF₂, CaF₂, LiF₂. Forming of such a fluoride on the surfaceof the hydrogen containing material is effective in increasing ofactivity thereof.

[0047] As treating solution for forming a metallic fluoride layer on thesurface of the hydrogen containing material, hydrofluoric acid aqueoussolution or hydrofluoric anhydride solution, or solution composed by atleast one of organic compounds such as piridine, triethlamine andisopopyl alcohol, and hydrofluoric anhydride is used. The abovedescribed metal is contacted with the treating solution or added at atemperature between −200° C. and 200° C., preferably between −40° C. and100° C., thereby melting ultrafine particles of the metal ion into thesolution in a described amount at least one of the conditions.

[0048] The hydrogen containing material is immersed in the treatingsolution including the metal to fluorinate the material. If the surfaceof the hydrogen containing material is excessively fluorinated, theinherent characteristics of the hydrogen containing material isdeteriorated. Therefore, in order to restrain the reaction, it ispreferable to use a solution containing a small amount of water. In thecase of the hydrofluoric acid aqueous solution, it is preferable to usethe solution having a molality of 70% or more. When the above describedother solutions are used, the molality is the same as the hydrofluoricacid aqueous solution.

[0049] Therefore, the hydrogen containing material is dried at atemperature between the room temperature and 500° C., preferably between100° C., and 250° C., purging with a gas such as Ar, N₂, He which hasnot a bad influence upon the fluorination treatment. Further, after theatmosphere of the hydrogen fluoride is discharged, the hydrogencontaining material undergoes heat treatment at the dry temperature ormore to stabilize the fluoride layer formed on the surface of thehydrogen containing material. By the heat treatment, the fluoride of themetal composing the hydrogen containing material itself and the metallicfluoride included in the treating solution are integrated, on thesurface of the hydrogen containing material.

[0050] In the above described process, the treating solution in thereaction vessel is vaporized by the heating of the solution, withoutseparating an excessive solution. If it takes long time for vaporizingthe treating solution having a low concentration of the ultrafineparticles of the metal ion and it is preferable to separate the treatingsolution. However, there may be occurred that the metal included in thetreating solution is formed on the surface of the hydrogen containingmaterial as a fluoride, dependent on the kind of the metal. Therefore itis preferable to select the concentration and to separate the excessivesolution in dependency on the kind of the hydrogen containing materialand the kind of the metal included in the treating solution.

[0051] The hydrogen containing material having the fluoride film on thesurface thereof by the above described process has a high activity tothe hydrogen molecule. Furthermore, even in the poisonous environment,the hydrogen containing material stably keeps the activity to thehydrogen.

[0052] There is difference in the form of the metal fluoride film formedon the surface of the hydrogen containing material in dependency on thekind of the hydrogen containing material and the kind of the metalincluded in the treating solution, as following examples.

[0053] (1) The fluoride of the metal composing the hydrogen containingmaterial is formed on the surface of the material, and the metalincluded in the treating solution becomes fluoride, the fluoride film isformed in the condition that both fluorides are mingled together.

[0054] (2) After the fluoride of the metal composing the hydrogencontaining material has been formed on the surface of the material, themetal included in the treating solution becomes fluoride which is formedon the metal fluoride.

[0055] (3) The metal of the surface of the hydrogen containing materialis fluorinated and melted in the treating solution, and the melted metalfluoride is formed again on the surface of containing material as afluoride film together with the metal in the treating solution when thesolution is dried.

[0056] Although it is preferable that the all surface of the hydrogencontaining material is coated with the fluoride of the metal, it isallowable that the,hydrogen containing materials are contacted with eachother so that the contacted surfaces are not covered by the fluoride. Ifthe active fluoride exists only on a part of the surface of the hydrogencontaining material, it is possible to maintain high reactivity.

[0057] The depth and other conditions of the fluoride of the metal ofthe hydrogen containing material can be properly adjusted by adjustingthe treatment period of time, treating temperature and others inaccordance with the use of the hydrogen containing material. Further,there is a case that metals other than fluorine, the hydrogen containingmaterial and metals included in the treating solution are included inthe fluoride film formed on the hydrogen containing material. Forexample, treated in such an environment as atmosphere where the surfaceof the hydrogen containing material is oxidized and hydroxided, oxideand hydroxide are formed. Therefore, in the compound layer formed on thesurface of the hydrogen containing material, compounds such as M, O—M,F—M, F—O—M (F: fluorine, O: oxygen, M: metal) are mingled in astoichiometrically stable condition or in a stoichrometrically unstable(non-stoichiometric composition). There may be a case where otherelements other than metals included in the treating solution areincluded in the fluoride film on the surface of the hydrogen containingmaterials.

[0058] Although there is a case where the fluoride film is formed insubstantially uniform thickness, there is a case that partialprojections are formed on the film. In either case, the hydrogencontaining material as the matrix becomes fluoride and a gradientdiffusion layer of the hydrogen containing material and the fluoride isformed in the boundary layer between the hydrogen containing materialsand the fluoride. (In the boundary layer, the fluorine concentrationreduces toward the inside and the concentration of the metal composingthe hydrogen containing material increases in reverse.)

[0059] Therefore, the fluoride on the hydrogen containing material iskept in a stable condition without peeling off despite the expansion andcontraction caused by the containing and discharging of the hydrogen.The surface of the hydrogen containing materials is finely powdered bythe containing and discharging of the hydrogen. Therefore if thecontaining and discharging is repeated a neo-surface (metal surface) isexposed. However, if a fluoride having a high activity exists on a partof the hydrogen containing material, it is possible to maintain a highreactivity.

[0060] As described above, a film consisting a metal fluoride as a maincomponent on the surface of the hydrogen containing material by treatingwith the hydrofluoric acid aqueous solution or hydrofluoric anhydridesolution or solution composed by at least one of organic compounds suchas piridine, triethlamine and isopopyl alcohol, and hydrofluoricanhydride. Therefore, the hydrogen containing material has a highactivity with the hydrogen element. In the prior art, in order toinitially activate the hydrogen containing material, the material mustbe treated,at a high temperature and a high pressure and in a highvacuum.

[0061] In accordance with the present invention, the hydrogen containingmaterials can be initially activated without high temperature, highpressure, and high vacuum. Furthermore, since the fluoride film formedon the surface is a stable compound layer, there is no danger ofignition of the hydrogen containing material in the atmosphere. Sincethe hydrogen containing material having the fluoride film has apoisoning restraining effect other than the hydrogen element, the dangerproblem at the treatment of the hydrogen containing material is solved.As a result, the upkeep for installations, production and transportationcan be largely reduced. Since the fluoride film is formed by thereaction in the solution of high concentration or in the anhydridesolution, a large installation and complicated technique in the reactiontreatment are not necessary. Both of the high activation and thestabilization treatment of the hydrogen containing material which can bemass produced can be carried out at the same time.

EXAMPLE I

[0062] The alloy TiFe_(0.8)Mn_(0.2) as the hydrogen containing materialwas mechanically powder and classified into less than 250 μm by ascreen. The alloy powdered of 100 g was put in a first reaction vessel.On the other hand, the alloy LaNi_(4.7)Al_(0.3) was mechanicallypowdered and classified into less than 38 μm, and the alloy powder of100 g was put in a second reaction vessel. More than 9N high-purityhydrofluoric anhydride solution of 100 cc was poured in the secondreaction vessel and kept for three minutes at a temperature of about 80°C. Thereafter, while the powder LaNi_(4.7)Al_(0.3) was filtered by afilter paper, the hydrofluoric anhydride solution was transferred to thefirst reaction vessel in which the powder of TiFe_(0.8)Mn_(0.2) is put.The first reaction vessel was put in a constant temperature tank heatedat 100° C. and N₂ gas was flowed in the first reaction vessel tovaporize the hydrofluoric anhydride solution, thereby drying the vessel.After the drying, the temperature of the constant temperature tank wasincreased to 150° C. and kept for one hour to heat-treat the alloy.Thereafter, the hydrogen containing material was cooled to approximatelyroom temperature, while N₂ gas was flowed in the first reaction vessel.The hydrogen containing material was taken out from the first reactionvessel. Thus, the alloy powder TiFe_(0.8)Mn_(0.2) having a fluoride filmin which F, La, Al and Ni are formed on the surface of the powder in themingled condition was obtained.

[0063] According to the observation of the surface of the alloyTiFe_(0.8) Mn_(0.2) with a scanning electron microscope, protrusiveproduct of about 0.1-0.3 μm, was formed on the surface. It was confirmedthat there is existed F, La, Al, Ni which do not exist in the untreatedalloy on the surface in the mingled condition, as a result of theelement analysis of the surface of the alloy after the treatment with anenergy dispersion type X-ray analysis device. The elements melted in thehydrofluoric anhydride solution in the second reaction vessel wereanalyzed with an inductive coupling plasma light emitting analyzingdevice.

[0064] The Table 1 shows the result of the analysis and proportions ofthe molten elements. As a result, La and Al are melted more than theratio by mass of the original alloy LaNi_(4.7)Al_(0.3). The proportionsare approximately equal to the proportions of quantitative analysisresult of La, Ni, Al where Ti, Fe, Mn are removed by the energydispersion type X-ray analysis device. Therefore, it is considered thatthe metal ion of the molten LaNi_(4.7)Al_(0.3) in the hydrofluoricanhydride becomes a compound with fluorine and is finally stuck on thealloy powder TiFe_(0.8)Mn_(0.2) in the treatment of the vaporizing ofthe hydrofluoric anhydride. TABLE 1 Analysis Proportion of ProportionProportion LaNi_(4.7)A1_(0.3) (ppm) (%) La 32.8 24.0 42.3 Ni 65.2 30.754.0 A1 1.9 2.1 3.8

COMPARATIVE EXAMPLE 1a

[0065] A hydrofluoric anhydride in which alloy powder LaNi_(4.7)Al_(0.3)is not melted was used for highly activating the alloyTiFe_(0.8)Mn_(0.2) in the same method and condition as the example I.

COMPARATIVE EXAMPLE 1b

[0066] The alloy TiFe_(0.8)Mn_(0.2) was mechanically powdered andclassified into less than 250 μm and the fluoridization was not carriedout.

[0067] Evaluation

[0068] Initial activation characteristics of TiFe_(0.8)Mn_(0.2) of theexample I, comparative examples 1a and 1b were evaluated in the sameconditions and compared. The transverse of FIG. 1 shows time necessaryfor containing hydrogen, and the vertical line shows the quantity ofcontained hydrogen, in the case that a maximum containing quantity of anuntreated alloy is set to 100%.

[0069] As the reaction conditions, the air in the reaction vessel wasdischarged by the evacuation at the alloy temperature of constant 80° C.until the inside pressure becomes 1 Pa, and the vacuum discharge wasfurther continued for thirty minutes, and then hydrogen was introducedat the initial pressure of 2.5 MPa. On the other hand, all test pieceswere left in the atmosphere controlled at the temperature of 25° C. andthe humidity of 30% for 24 hours. The results are as follows.

[0070] The untreated alloy TiFe_(0.8)Mn_(0.2) of the comparative example1b did not absorb the hydrogen despite the passage of 6 hours.

[0071] The alloy of the comparative example 1a started to absorb thehydrogen at the time of one-hour passages and contained quantity ofabout 100% of the hydrogen after 5 hours.

[0072] On the other hand, the alloy of the example I started to absorbthe hydrogen after 30 minutes, and contained quantity of almost 100% ofthe hydrogen after 2.5 hours.

[0073] Although the alloy of the comparative example 1a also has a highreactivity with hydrogen compared with the untreated alloy of thecomparative example 1b, the alloy of the example I has a more higherreactivity than the comparative example 1a.

[0074] As a modification of the example I , the alloy MmNi_(4.5)Al_(0.5)was used instead of the alloy LaNi_(4.7)Al_(0.3), and the same treatmentas the example I was carried out. In accordance with the evaluationsimilar to the example I, it was confirmed that the same effects as theexample I were achieved.

[0075]FIG. 2 shows the fact that the test piece treated by the example Ihas a poisoning restraining effect against the poison of the poisonousmaterials other than the hydrogen element, compared with comparativeexamples 1a and 1b. The transverse of FIG. 2 shows the number of thecycles of the containing and discharging of hydrogen, the vertical lineshows the ratio of the change of the hydrogen containing quantity in thecase that the initial hydrogen containing quantity is set to 100% whenthe high purity hydrogen of 7N is used.

[0076] As the activation treatment before the test, the air in thetreating vessel, in which the alloys of the example I and of thecomparative examples are contained, was discharged by the evacuationuntil 1 Pa at 80° C. Thereafter, the high purity hydrogen gas of 7N wasintroduced in the reaction vessel at the introduction pressure of 3 MPa.The activation treatment was carried out 5 times. After the activationtreatment, in order to confirm the initial hydrogen containing quantity,the 7D high purity hydrogen gas including CO of 1,044 ppm was introducedat the introduction pressure of 3 MPa at 80° C. for 10 minutes, so thatthe hydrogen is to be included in the test piece. The obtained value bythe treatment was used as the initial hydrogen containing quantity.Thereafter, poisoning test was carried out. In the poisoning test, thesame treatment as the above described initial hydrogen containingtreatment was performed. After the poisoning test, the hydrogen in thereaction vessel was spontaneously emitted at 80° C. Until the pressurein the vessel becomes 12 MPa, and the change of the hydrogen containingquantity was confirmed at every cycle.

[0077] The hydrogen containing quantity of the untreated alloy of thecomparative example 1b decreased to 23% at the first cycle and to 0% atthe second cycle. Although the hydrogen containing quantity of thecomparative example 1a decreased to 56% at the tenth cycle, the alloyhad a poisoning restraining effect compared with the comparative example1b.

[0078] On the other hand, the alloy of the example I maintained thehydrogen containing quantity more than 90% at the tenth cycle. In otherwords, the alloy has a great poisoning restraining effect.

[0079] As a result of the analysis of gas components at the emission bythe gas chromatography, there was confirmed that CH₄ was included in theemission gas of the example I and CO was less than the detection lowerlimit. In the comparative example 1a, both of CH₄ And CO were detected.In the alloy of the comparative example 1b, it was considered thathydrogen is scarcely emitted from the alloy. However, it was confirmedthat CO having a higher concentration than the original gas was includedin the hydrogen gas in the reaction vessel. Therefore, it is regardedthat in the poisoning restraining effect of the hydrogen containingalloy of the present invention, CO as the poisoning element ishydrogenized to be converted to CH₄ so that the CH₄ is removed from thesurface of the alloy.

EXAMPLE II

[0080] The alloy Zr(Fe_(0.75)Cr_(0.25))₂ as the hydrogen containingmaterial was mechanically powder and classified into less than 250 μm bya screen. The alloy powder of 100 g was put in a first reaction vessel.On the other hand, the element Al was mechanically powdered andclassified into less than 100 μm, and the alloy powder of 100 g was putin a second reaction. More than 9N high-purity hydrofluoric anhydridesolution of 200 cc was poured in the second reaction vessel and kept forthree minutes at a temperature of about 120° C. Thereafter, while thepowder Al was filtered by a filter paper, the hydrofluoric anhydridesolution was transferred to the first reaction vessel in which thepowder of Zr(Fe_(0.75)Cr_(0.25))₂ is put. The first reaction vessel wasput in a constant temperature tank heated at 80° C. and N₂ gas wasflowed in the first reaction vessel to vaporize the hydrofluoricanhydride solution, thereby drying the vessel. After the drying, thetemperature of the constant temperature tank was increased to 120° C.and kept for one hour to heat-treat the alloy. Thereafter, the hydrogencontaining material was cooled to approximately room temperature, whileN₂ gas was flowed in the first reaction. The hydrogen containingmaterial was taken out from the first reaction vessel. Thus, the alloypowder Zr (Fe_(0.75)Cr_(0.25))₂ having a fluoride film of Al on thesurface of the powder was obtained.

[0081] According to the observation of the surface of the alloyZr(Fe_(0.75)Cr_(0.25))₂, it was confirmed that there is existed FAlwhich do not exist in the untreated alloy as a result of the elementanalysis of the surface of the alloy Zr (Fe_(0.75)Cr_(0.25))₂ after thetreatment with an energy dispersion type X-ray analysis device.

COMPARATIVE EXAMPLE 2a

[0082] A hydrofluoric anhydride in which alloy powder Al is not meltedwas used for highly activating the alloy Zr (Fe_(0.75)Cr_(0.25))₂ in thesame method and condition as the example II.

COMPARATIVE EXAMPLE 2b

[0083] The alloy Zr (Fe_(0.75)Cr_(0.25))₂ was mechanically powdered andclassified into less than 250 μm and the fluoridization was not carriedout.

[0084] Evaluation

[0085] Initial activation characteristics of Zr(Fe_(0.75)Cr_(0.25))₂ ofthe example II, comparative examples 2a and 2b were evaluated in thesame conditions and compared. The transverse of FIG. 3 shows timenecessary for containing hydrogen, and the vertical line shows thequantity of contained hydrogen, in the case that a maximum containingquantity of an untreated alloy is set to 100%.

[0086] As the reaction conditions, the air in the reaction vessel wasdischarged by the evacuation at the alloy temperature of constant 60° C.until the inside pressure becomes 1 Pa, and the vacuum discharge wasfurther continued for thirty minutes, and then hydrogen was introducedat the initial pressure of 1.5 MPa at 60° C. On the other hand, all testpieces were left in the atmosphere controlled at the temperature of 25°C. and the humidity of 30% for 24 hours. The results are as follows.

[0087] The untreated alloy Zr(Fe_(0.75)Cr_(0.25))₂ of the comparativeexample 2b did not absorb the hydrogen despite the passage of 6 hours.

[0088] The alloy of the comparative example 2a started to absorb thehydrogen at the time of 1.5-hour passage, and contained quantity ofabout 100% of the hydrogen after 4.5 hours.

[0089] On the other hand, the alloy of the example II started to absorbthe hydrogen after one hour, and contained quantity of almost 100% ofthe hydrogen after 3 hours.

[0090] Although the alloy of the comparative example 2a also has a highreactivity with hydrogen compared with the untreated alloy of thecomparative example 2b, the alloy of the example II has a more higherreactivity than the comparative example 2a.

[0091] As a modification of the example II, Fe, Mg, Ca or Li was usedinstead of Al and the same treatment as the example II was carried out.In accordance with the evaluation similar to the example II, it wasconfirmed that the same effects as the example II were achieved.

[0092] The test of the poisoning restraining effect of the hydrogencontaining material of the example II was carried out in the same manneras the example I. As a result of the test, it was confirmed that thehydrogen containing material of the example II has a great poisoningrestraining effect although there are individual differences, and CH₄ isincluded in any emitted hydrogen gases.

EXAMPLE III

[0093] The alloy V(vanadium) as the hydrogen containing material wasmechanically powder and classified into less than 75 μm by a screen. TheV powder of 10 g was put in a first reaction vessel. On the other hand,Mg was mechanically powdered and classified into less than 250 μm, andMm was mechanically powdered and classified into less than 1 mm and Mgpowder 15 g and Mm powder 15 g were put in a second reaction vessel.More than 9N high-purity hydrofluoric anhydride solution of 100 cc waspoured in the second reaction vessel and kept for three minutes at atemperature of about 100° C. Thereafter, while the powders Mg and Mmwere filtered by a filter paper, the hydrofluoric anhydride solution wastransferred to the first reaction vessel in which the powder of V isput. The first reaction vessel was put in a constant temperature tankheated at 50° C. and N₂ gas was flowed in the first reaction vessel tovaporize the hydrofluoric anhydride solution, thereby drying the vessel.After the drying, the temperature of the constant temperature tank wasincreased to 120° C. and kept for one hour to heat-treat the powders.Thereafter, the hydrogen containing material was cooled to approximatelyroom temperature, while N₂ gas was flowed in the first reaction. Thehydrogen containing material was taken out from the first reactionvessel. Thus, the V powder having a fluoride film of Mg and Mm wasobtained.

[0094] According to the observation of the surface of V, it wasconfirmed that there is existed F which does not exist in the untreatedalloy Mg and La, Ce, Pr, Nd and Sm which are component elements of Mm,as a result of the element analysis of the surface of the alloy afterthe treatment with an energy dispersion type X-ray analysis device.

COMPARATIVE EXAMPLE 3a

[0095] A hydrofluoric anhydride in which Mg and Mm are not melted wasused for highly activating V powder in the same method and condition asthe example III.

COMPARATIVE EXAMPLE 3b

[0096] The vanadium V was mechanically powdered and classified into lessthan 75 μm and the fluoridization was not carried out.

[0097] Evaluation

[0098] Initial activation characteristics of the example III,comparative examples 3a and 3b were evaluated in the same conditions andcompared. The transverse of FIG. 4 shows time necessary for containinghydrogen, and the vertical line shows the quantity of containedhydrogen, in the case that a maximum containing quantity of an untreatedalloy is set to 100%.

[0099] As the reaction conditions, the air in the reaction vessel wasdischarged by the evacuation at the alloy temperature of constant 60° C.until the inside pressure becomes 1 Pa, and the vacuum discharge wasfurther continued for thirty minutes, and then hydrogen was introducedat the initial pressure of 1.5 MPa at 60° C. On the other hand, all testpieces were left in the atmosphere controlled at the temperature of 25°C. and the humidity of 30% for 24 hours. The results are as follows.

[0100] The untreated V of the comparative example 3b did not absorb thehydrogen despite the passage of 6 hours.

[0101] The vanadium V of the comparative example 3a started to absorbthe hydrogen at the time of three-hour passage, and contained quantityof about 80% of the hydrogen after 6 hours.

[0102] On the other hand, V of the example III started to absorb thehydrogen after two hours, and contained quantity of almost 100% of thehydrogen after 5 hours.

[0103] Although the alloy of the comparative example 3a also has a highreactivity with hydrogen compared with the untreated alloy of thecomparative example 3b, the vanadium of the example III has a morehigher reactivity than the comparative example 3a.

[0104] The test of the poisoning restraining effect of the hydrogencontaining material of the example III was carried out in the samemanner as the example I. As a result of the test, it was confirmed thatthe hydrogen containing material of the example II has a great poisoningrestraining effect although there are individual differences, and CH₄ isincluded in any emitted hydrogen gases.

[0105] An additional evaluation was carried out about the condition ofthe fluoride layer of the highly activated hydrogen containing materialof the example I. As a comparative example 1c, the highly activatedhydrogen containing material described in the Japanese Patent Laid OpenPublication 10-219301 as an example 5 was used.

[0106] Fine particle test pieces of LaNi which were obtained by thehydrogenizing and dehydrogenizing were classified into diameters of25-50 μm by a filter. As the powder of alumimun fluoride, alumina powderof purity of 2N and diameter of 1 μm produced by the High PurityChemical Laboratory Co. Ltd. was used. The alumina powder was immersedin the hydrofluoric anhydride solution at the room temperature for onehour and dried in the atmosphere of nitrogen gas of 393 K for one hour.The surfaces of LaNi powder test pieces by the obtained aluminumfluoride powder were improved by the shock method by the high speed aircurrent using NHS—O type produced by the Nara Machine Production Co.Ltd. More particularly, aluminum fluoride powder and LaNi₅ of 20 g werecharged in the mixer in the capacity ratio of 1 to 50, and mixed at therotating speed of 1,500 rpm for ten minutes to produce a mixture. Thequality of the mixture of 10 g was improved at the rotating speed of15,000 rpm for 15 hours, thereby to produce capsule particles each ofwhich comprises LaNi₅ with a cover of the aluminum fluoride.

[0107] In the evaluation, 10 g of each of the alloys of the example Iand comparative example 1a were put in respective reaction vessels andevacuated up to 0.5 Pa at the temperature of 80° C., and high purityhydrogen of 7N was supplied to each reaction vessel at the pressure of2.5 MPa for 15 minutes. Furthermore, each reaction vessel was evacuatedat the same temperature up to 1 Pa. Regarding the high purity hydrogensupply and the evacuation as one cycle, 1,000 cycles of discharge andsupply were carried out. As the result of the observation of the surfacecondition of the alloy with the electron microscope, there are releasedportions of the fluoride film on the surface of the alloy of thecomparative example 1c as shown in FIG. 6. To the contrary, in the alloyof the example I although cracks were observed, released portions werenot observed as shown in FIG. 5.

[0108] In accordance with the present invention, in the cases that alarge amount of metals which become high active when fluorinated areincluded in the basic composition elements, that a small amount ofmetals which become high active are included in the compositionelements, or that highly activated metal is not included, in any case,it is possible to form a large amount of very highly activated fluoridelayers, compared with a hydrogen containing material which is simplytreated by fluorine, on the surface of the hydrogen containing material.

[0109] In the boundary surface between the hydrogen containing materialas the matrix and the fluoride, a compound layer in which theconcentration of elements composing the matrix and the concentration ofthe fluoride are changed in inclined conditions is formed. The surfaceof the material is in the condition the fluoride of the matrix and thefluoride of the highly activated metal are mingled.

[0110] In another case, in the boundary surface between the hydrogencontaining material as the matrix and the fluoride, a compound layer inwhich the concentration of elements composing the matrix and theconcentration of the fluoride are gradually changed in inclinedconditions is formed, and the fluoride of the matrix is formed on theouter surface of the compound layer, and further on the outside of theouter surface, the fluoride of the highly activated metal is formed.

[0111] By forming the fluoride layer of metal the concentration of whichchanges in inclined condition, it is possible to prevent the metallicfluoride from exfoliating from the hydrogen containing material.Therefore, it is possible to maintain high activity with hydrogen for along term in spite of a poisoning environment, while maintaining atleast one of durability of the hydrogen containing material itself and alarge capacity for absorbing hydrogen.

[0112] Furthermore, in accordance with the method for producing hydrogencontaining material of the present invention, by contacting thetreatment liquid for fluorinating the metal and the hydrogen containingmaterial with each other, the metallic fluoride is formed on the surfaceor on the surface portion of the hydrogen containing material.Therefore, it is possible to produce the hydrogen containing material bya simple device with ease, and to correspond to the mass production.Thus, it is possible to easily form fluoride having a high activity withhydrogen and having a characteristic for preventing the exfoliation ofthe fluoride.

[0113] While the invention has been described in conjunction withpreferred specific embodiment thereof, it will be understood that thisdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the following claims.

What is claimed is
 1. A hydrogen containing material comprising: a firstcompound including hydrogen containing material and fluoride; a secondcompound including a metal which becomes highly reactive with hydrogenwhen the metal becomes a compound including fluorine, and a compoundincluding fluorine, wherein the first compound and the second compoundare integrally formed into a one-piece layer on the surface of thehydrogen containing material.
 2. The material according to claim 1wherein the hydrogen containing material comprises a material orintermediate product or finished product of an alloy selected from thegroup consisting of a zirconium alloy, titanium alloy, vanadium alloy,rare earth alloy, and magnesium alloy.
 3. The Material according toclaim 1 wherein the metal which becomes highly reactive with hydrogenwhen the metal becomes a compound including fluorine is at least onemetal selected from a rare earth metal, rare earth alloy, Fe, Al, Mg,Ca, Mn, Zn, Zr, Li, or alloys comprising these elements.